Decisiveness is her strength, her weakness is her children, and her wish is for a better tennis backhand. This is Anna Wintour, editor-in-chief of Vogue for twenty years, being interviewed on R. J. Cutler’s documentary, The September Issue, which was Vogue’s 2007 biggest issue ever, reaching thirteen million readers, and weighing over four pounds with 840 pages (727 are ad pages!). Let’s call the film, The Voyeurs Issue, as Cutler weaves us through the behind-the-scenes shenanigans. But this long day’s journey into the arduous months of creating this extraordinary tome may beguile fashionistas and fashion freaks, although it borders, at times, on tedium.

Fortunately, the Welsh-born creative director Grace Coddington, a Victoriana portrait with her massive red hair, spares us some longueurs with her chilly comments and witty insights. She makes no bones about disagreements with Anna, who confides that Grace is remarkable. One suspects that without Grace’s imaginative moxie, where would Vogue be? Grace gives Anna full credit for being ahead of the celebrity culture, and choosing celebrities, early on, for Vogue’s covers.

But do we really give a fig about Anna requesting that Sienna Miller’s neck be photoshopped for Mario Testino’s cover photograph? Still, one sympathizes with Neiman Marcus chief Burt Tansky admonishing Anna to address the situation of late deliveries, and possibly wring a few designers’ necks. Karl Lagerfeld, Oscar de la Renta, Jean Paul Gaultier and Yves Saint Laurent’s Stefano Pilati are given short shrift with meaningless cameos, but their models do dress up the liturgical pacing. The exuberant and delightful editor-at-large, Andre Leon Talley, registers as a zero.

Anna’s daughter Bee Shaffer reveals that fashion doesn’t interest her, that “there’s more to life than fashion, which is weird.” Bee’s goal was a career in law, but recently changed to theater. Anna’s is a teen model’s body, her charm-on-camera factor is down pat, although her voice is flat. Her lips are cute, sexy and kissable, but that slick pageboy hairstyle becomes, in Eartha Kitt’s phrasing of a lyric, “monotone-eee-ous” during the film’s 88 minutes. Oh, well, it’s her signature, without a hair ever out of place.